Molecular Cloning and Characterization of a Lysophosphatidic Acid Receptor, Edg-7, Expressed in Prostate

• Published in: Molecular pharmacology 2000-04, Vol.57 (4), p.753-759
• Main Authors: Im, D S, Heise, C E, Harding, M A, George, S R, O'Dowd, B F, Theodorescu, D, Lynch, K R
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Cells, Cultured; Cloning, Molecular; DNA; Humans; Male; Molecular Sequence Data; Prostate - metabolism; Rats; Receptors, Cell Surface - biosynthesis; Receptors, Cell Surface - genetics; Receptors, G-Protein-Coupled; Receptors, Lysophosphatidic Acid; Sequence Homology, Amino Acid
• ISSN: 0026-895X; 1521-0111
• DOI: 10.1124/mol.57.4.753

Two G protein-coupled receptors (Edg-2) and (Edg-4) for the lysolipid phosphoric acid mediator lysophosphatidic acid have been described by molecular cloning. However, the calcium-mobilizing receptor Edg-4 is not expressed in some cell lines that exhibit robust calcium responses to this ligand, thus predicting the existence of additional receptor subtypes. We report here on the characterization of a third human lysophosphatidic acid receptor subtype, Edg-7, which mediates lysophosphatidic acid-evoked calcium mobilization. In a rat hepatoma Rh7777 cell line that lacks endogenous responses to lysophosphatidic acid, this lipid mediator, but not others, evokes calcium transients when the cells have been transfected with Edg-7 or Edg-4 DNAs. Furthermore, frog oocytes exhibit a calcium-mediated chloride conductance in response to mammalian-selective lysophosphatidic acid mimetics after injection of Edg-7 mRNA. Edg-7-expressing Rh7777 cells do not show inhibition of forskolin-driven rises in cAMP in response to lysophosphatidic acid. However, membranes from HEK293T cells cotransfected with Edg-7 and G i2 α protein DNAs show lysophosphatidic acid dose-dependent increases in [γ- 35 S]GTP binding with an EC 50 value of 195 nM. When we used this assay to compare various synthetic LPA analogs at Edg-2, Edg-4, and Edg-7 receptors, we found that ethanolamine-based compounds, which are full LPA mimetics at Edg-2 and Edg-4, exhibit little activity at the Edg-7 receptor. Edg-7 RNA was detected in extracts of several rat and human tissues including prostate. Together, our data indicate that Edg-7 is a third lysophosphatidic acid receptor that couples predominantly to G q/11 α proteins.